Internal parasite in my Coral Beauty?

[GrotonReefer]

New to posting so hoping I get this right.

Just re-setting up my 180 mixed reef tank after moving. Previous tank was killer with over 50 corals and bunch of fish (tangs, wrasses, etc). Now starting to stock after a complete reboot. Successfully put in 9 firefish after 4 w quarantine and then got a scopus, clowns, dottyback, and a coral beauty from a reputable on-line dealer. Did tank transfer method (TTM) 3 days X 4 but noticed all fish getting clamped fins and flashing during the 4th transfer. Suggestive of velvet or brook (learned about these the hard way) so did a freshwater dip for all and moved to a 29 gallon hospital tank with 2.25 ppm copper (Copper Power) with Hanna's copper checker. Stinks I couldn't snag some CP. Fish doing much much better EXCEPT for two remaining observations leading to following questions:

1. Scopus, clowns, and dottyback much much happier after a week; however, still see some flashing behavior. Is this a continuing effect from an original infection OR does this indicate some other ongoing disease?

2. This is the really weird one: The coral beauty has developed a strange protruding white/clear spike coming out of its anus (see the pic). I think it was actually there during the TTM. Seems like it is some sort of internal parasite and wanted to get some confirmation from someone who might have seen this before.

3. If it is some sort of worm, etc, how should it be treated?

4. And will the other fish that have been with the coral beauty have become infected?

Thanks for any help!